1. Field of the Invention
The present invention relates to implantable vascular access devices used in the delivery and/or withdrawal of fluids to and from the body and more particularly relates to a self-sealing device which permits intermittent vascular access.
2. Description of the Prior Art
Conventional vascular access devices are surgically implanted under the skin to allow for intermittent access to a selected vascular structure, such as an artery or a vein, for introducing and/or withdrawing fluids to and from the selected vascular structure. Typically, such devices generally include an interior chamber having an outlet opening connected via a cannula to a vascular structure within the body and a penetrable membrane which serves as a cover for the interior chamber of the device. The penetrable membrane or septum is comprised of a material, such as silicone rubber, which automatically reseals itself after being penetrated by a hypodermic needle or a needle introduced catheter.
In operation, a needle passes through the skin and through the penetrable membrane into the interior chamber allowing fluid to be injected into the chamber and expelled through the cannula into the selected vascular structure or, conversely, fluid may be withdrawn. The advantages of an implantable device over acute catheter procedures are reduced infection, easier patient maintenance and improved aesthetics. Typical implantable vascular access devices are shown in U.S. Pat. No. 5,318,545 to Tucker and U.S. Pat. No. 5,755,780 to Finch, Jr. et al.
The advancement of modem hemodialysis procedures have brought with it the development of vascular access devices for the purpose of acquiring and returning large quantities of blood for passage through a hemodialysis unit. To facilitate adequate dialysis flow rates, relatively large diameter needles and/or catheters in the range of 14 gauge or higher are required. A major drawback of conventional vascular access devices, particularly those used in hemodialysis procedures, is the deterioration of the rubber membranes resulting from repeated penetration with such large gauge needles. Additionally, typical vascular access devices provide for only one needle port resulting in chronic breach of the skin at the same location. This in turn results in increased skin trauma and possible infection.
Accordingly, it is desirable to provide a vascular access device which can withstand multiple insertions with a large diameter needle and which provides reduced skin trauma and easier patient maintenance.